Images can contain a vast amount of visual information. However, the visual information typically does not convey many of the details associated with capturing the image. Therefore, text-based image metadata can be recorded and stored along with an image, such as in an image file header. Image metadata is structured data that describes characteristics of an image. Further, because the image metadata is text-based, it can be used to easily identify and manage images
When an image is captured, image metadata also can be captured, such as by a processor included in the image capture device. The captured image metadata can include generic information as well as camera-manufacturer specific information. Each item of metadata is known as a property and describes a particular characteristic associated with the image. A property can describe any characteristic that can be ascertained and expressed textually or numerically. For example, properties can include the time and date of capture, the location of capture, dimensions of the image, and one or more technical settings or values relating to the image capture device.
Further, image metadata can be organized in a data structure, such as a list or an array. As a result, the image metadata can be accessed and processed by a computer. In some instances, image metadata can be organized hierarchically, so that one or more items of metadata are categorized under one or more other items. In other instances, image metadata can be organized using a single-level list of related and/or unrelated properties. Additionally, image metadata can be expressed as attribute-value pairs.
Numerous standards have been developed for organizing metadata associated with photographs. For example, the International Press Telecommunications Council (IPTC) created the IPTC Photo Metadata definition, which can be used to describe and administrate photographs. IPTC Photo Metadata groups image metadata into categories relating to administrative, descriptive, and rights related properties. Further, the Japan Electronic Industries Development Association created the Exchangeable image file format (Exif) specification that defines an image file format for use by digital cameras. The Exif standard incorporates metadata tags relating to a wide variety of properties including camera settings, date and time information, copyright information, and a thumbnail.
Once image metadata has been generated and stored in association with an image, the metadata remains with that image. For example, the image metadata can be transferred or copied when the corresponding image is transferred or copied. Image metadata also can be automatically or manually edited. For example, an existing property can be altered or deleted if it is incorrect. Further, new metadata can be appended to the metadata associated with an image file. Thus, metadata that was not available to the image capture device at the time of capture nonetheless can be associated with the image.